Wang et al. reported the stimulatory effect of ox-LDL on the expression of Lp-PLA2 in monocytes, which are a primary source of this enzyme. These recent findings in animal and in vitro studies may provide insight into the interaction between Lp-PLA2 Clofentezine activity and oxidative stress in the context of atherosclerosis. Therefore, our aim was to study the relationship of Lp-PLA2 activity in plasma and the enzyme activity in supernatants from nonstimulated peripheral blood mononuclear cell cultures. Plasma ox-LDL and cytokine production from PBMCs in healthy nonobese women and also according to the menopausal status were evaluated. The major finding of this study is the lack of relation between circulating Lp-PLA2 activity and Lp-PLA2 activity in PBMCs in postmenopausal women with high ox-LDL. A significant increase in Lp-PLA2 activity in the plasma but not the PBMCs of postmenopausal women with high ox-LDL may indicate other sources of Lp-PLA2 production except PBMC. The extent of the increase in plasma Lp-PLA2 may depend not only on the levels of lipoproteins carrying Lp-PLA2 in circulation but also on the cellular synthesis of this enzyme. Monocytes, macrophages, T-lymphocytes, mast cells, and liver cells are known as the main sources of Lp-PLA2. Recently, Keyzer et al. found increased circulating LpPLA2 activity with increased ox-LDL levels in hypercholesterolemic pigs and the main source of increased circulating Lp-PLA2 activity were plaque macrophages. Therefore, the LpPLA2 production in plaque macrophages could partly explain the positive correlation of circulating Lp-PLA2 activity with plasma ox-LDL but not with Lp-PLA2 activity in PBMCs from postmenopausal women with high ox-LDL in this study. However, we could not measure Lp-PLA2 activity in plaque macrophages, or the plaque or intima itself, where it may be of most biological relevance. Lp-PLA2 is thought to play an atherogenic role by hydrolyzing oxidized phospholipids in ox-LDL, resulting in the generation of two bioactive lipid mediators, lysophosphatidyl choline, and oxidized free fatty acids. The biological role of LpPLA2 is also controversial; initial reports indicated an antiatherogenic effect, whereas growing evidence has demonstrated a role for Lp-PLA2 as a proinflammatory molecule and an independent risk factor for CVD. Lp-PLA2 belongs to the expanding superfamily of Succinylsulfathiazole structurally diverse phospholipase A2 enzymes, also known as PAF-AH. It travels mainly with LDL in the blood, and less than 20% is associated with HDL. In mice, the majority of plasma PAF-AH is bound to HDL, this was considered as possible antiatherogenic effect. In human atherosclerotic lesions, two main sources of Lp-PLA2 were identified in human atherosclerotic lesions, including that which is brought into the intima bound to LDL from the circulation, and that which is synthesized de novo by plaque inflammatory cells.